36 Nontranslational Functions of Components of the Translational Apparatus

Abstract

A growing number of studies have identified new and often nontranslational functions for many components of the translational apparatus, including tRNAs, aminoacyl-tRNA synthetases, ribosomal proteins, and initiation and elongation factors (Fig. 1). Although initially the sheer abundance of some of these components made their identification in novel functions suspect, increasingly detailed biochemical and genetic studies have established the multifunctional nature of these molecules. The studies include classic and elegant examples of viral systems that recruit host factors for their replication and maintenance, as well as cellular processes that adapt these abundant cellular components to new and perhaps related functions. Furthermore, the increasing recognition that some translational components reside in previously unexpected locations may serve to link the regulation of gene expression and the quality of protein synthesis with new functions of the translational apparatus itself (Fig. 1).

Although beyond the scope of this chapter, it is a fascinating evolutionary question as to how these components came to perform other functions in addition to their translational roles. It seems likely that at least some viruses evolved to take advantage of these preexisting abundant components (see Chapter 8), but in cases where cellular functions are involved, it is not so obvious whether the translational or the other function came first. In this chapter, we briefly review the classic examples of nontranslational functions of components of the protein synthetic machinery while focusing on the newly emerging themes of nontranslational functions, and potential explanations of the varied and important roles these factors play in...